1. Field of the Invention
This invention relates generally to a method and apparatus for determining the channel to which a receiver is tuned, and more particularly, to a new and improved method and apparatus for identifying the channel number being displayed by a light emitting display on the receiver.
2. Description of the Prior Art
Various arrangements have been employed to determine the channel to which a television receiver is tuned. A disadvantage of many known monitoring arrangements is that an internal connection to the television receiver is required. For example, Haselwood et al. U.S. Pat. No. 3,973,206, issued on Aug. 3, 1976, discloses a method of determining the channel to which a receiver is tuned by monitoring the varactor diode tuning voltage. However, this type of monitoring requires that internal connections be made inside of the television receiver.
Another method for determining channel tuning is disclosed in Haselwood et al. U.S. Pat. No. 4,425,578, issued on Jan. 10, 1984. In connection with the method disclosed in that patent, a signal injection source and a detector/receiver are arranged so as to detect the combined signal from the injection signal source and a video carrier to which the video receiver is tuned. A significant drawback of signal injection monitoring arrangements of this type is the potential interference with the functional operation of the video receiver being monitored.
U.S. Pat. No. 4,723,302, issued on Feb. 2, 1988, discloses another method for determining channel tuning. This method utilizes a local oscillator frequency measurement of the monitored receiver. While this method is generally effective, the disclosed method and apparatus requires that a probe be positioned at a selected location in the monitored receiver. Consequently, physical access to the receiver is required.
Access to the tuning mechanism of a television receiver is becoming increasingly difficult. This is particularly the case with the advent of cable and pay television systems that utilize various converters and decoders, many of which are difficult to access. As a result, various other monitoring systems have been developed.
For example, Solar U.S. Pat. No. 4,764,808, issued on Aug. 16, 1988, discloses a method of determining the channel to which a receiver is tuned by detecting a horizontal sweep signal of the monitored receiver. The frequency of the detected sweep signal is compared to stored characteristic frequency values in order to determine the channel to which the receiver is tuned. Another example of a method used in determining the channel to which a receiver is tuned is disclosed in Kiewit U.S. Pat. No. 4,876,736, issued on Oct. 24, 1989. This method can be utilized when a remote control is being used to select the channel to which the receiver is tuned. The signal transmitted by the remote control is intercepted by a first receiver so that the desired channel can be stored. The first receiver than transmits an activating signal to the receiver.
These types of methods for determining the channel to which a receiver is tuned eliminates the necessity of actually gaining access to the receiver being monitored. However, the methods used in determining the channel to which the receiver is tuned are quite complex and/or only are usable if a remote control is utilized to change the channel to which the receiver is tuned.